[FFmpeg-devel] [PATCH 2/2] swscale/output: Bias 16bps output calculations to improve non overflowing range for GBRP16/GBRPF32
Mark Reid
mindmark at gmail.com
Thu Nov 3 00:55:01 EET 2022
On Wed, Nov 2, 2022 at 3:52 PM Mark Reid <mindmark at gmail.com> wrote:
>
>
> On Wed, Nov 2, 2022 at 2:03 PM Michael Niedermayer <michael at niedermayer.cc>
> wrote:
>
>> Fixes: integer overflow
>> Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
>> ---
>> libswscale/output.c | 25 +++++++++++--------------
>> libswscale/x86/output.asm | 16 +++++++++++++++-
>> 2 files changed, 26 insertions(+), 15 deletions(-)
>>
>> diff --git a/libswscale/output.c b/libswscale/output.c
>> index df4647adde..5c85bff971 100644
>> --- a/libswscale/output.c
>> +++ b/libswscale/output.c
>> @@ -2372,18 +2372,15 @@ yuv2gbrp16_full_X_c(SwsContext *c, const int16_t
>> *lumFilter,
>>
>> Y -= c->yuv2rgb_y_offset;
>> Y *= c->yuv2rgb_y_coeff;
>> - Y += 1 << 13;
>> + Y += (1 << 13) - (1 << 29);
>> R = V * c->yuv2rgb_v2r_coeff;
>> G = V * c->yuv2rgb_v2g_coeff + U * c->yuv2rgb_u2g_coeff;
>> B = U * c->yuv2rgb_u2b_coeff;
>>
>> - R = av_clip_uintp2(Y + R, 30);
>> - G = av_clip_uintp2(Y + G, 30);
>> - B = av_clip_uintp2(Y + B, 30);
>> + dest16[2][i] = av_clip_uintp2(((Y + R) >> 14) + (1<<15), 16);
>> + dest16[0][i] = av_clip_uintp2(((Y + G) >> 14) + (1<<15), 16);
>> + dest16[1][i] = av_clip_uintp2(((Y + B) >> 14) + (1<<15), 16);
>>
>> - dest16[0][i] = G >> 14;
>> - dest16[1][i] = B >> 14;
>> - dest16[2][i] = R >> 14;
>> if (hasAlpha)
>> dest16[3][i] = av_clip_uintp2(A, 30) >> 14;
>> }
>> @@ -2448,18 +2445,18 @@ yuv2gbrpf32_full_X_c(SwsContext *c, const int16_t
>> *lumFilter,
>>
>> Y -= c->yuv2rgb_y_offset;
>> Y *= c->yuv2rgb_y_coeff;
>> - Y += 1 << 13;
>> + Y += (1 << 13) - (1 << 29);
>> R = V * c->yuv2rgb_v2r_coeff;
>> G = V * c->yuv2rgb_v2g_coeff + U * c->yuv2rgb_u2g_coeff;
>> B = U * c->yuv2rgb_u2b_coeff;
>>
>> - R = av_clip_uintp2(Y + R, 30);
>> - G = av_clip_uintp2(Y + G, 30);
>> - B = av_clip_uintp2(Y + B, 30);
>> + R = av_clip_uintp2(((Y + R) >> 14) + (1<<15), 16);
>> + G = av_clip_uintp2(((Y + G) >> 14) + (1<<15), 16);
>> + B = av_clip_uintp2(((Y + B) >> 14) + (1<<15), 16);
>>
>> - dest32[0][i] = av_float2int(float_mult * (float)(G >> 14));
>> - dest32[1][i] = av_float2int(float_mult * (float)(B >> 14));
>> - dest32[2][i] = av_float2int(float_mult * (float)(R >> 14));
>> + dest32[0][i] = av_float2int(float_mult * (float)G);
>> + dest32[1][i] = av_float2int(float_mult * (float)B);
>> + dest32[2][i] = av_float2int(float_mult * (float)R);
>> if (hasAlpha)
>> dest32[3][i] = av_float2int(float_mult *
>> (float)(av_clip_uintp2(A, 30) >> 14));
>> }
>> diff --git a/libswscale/x86/output.asm b/libswscale/x86/output.asm
>> index 84e94baaf6..f943a27534 100644
>> --- a/libswscale/x86/output.asm
>> +++ b/libswscale/x86/output.asm
>> @@ -44,11 +44,13 @@ pd_yuv2gbrp_y_start: times 8 dd (1 << 9)
>> pd_yuv2gbrp_uv_start: times 8 dd ((1 << 9) - (128 << 19))
>> pd_yuv2gbrp_a_start: times 8 dd (1 << 18)
>> pd_yuv2gbrp16_offset: times 8 dd 0x10000 ;(1 << 16)
>> -pd_yuv2gbrp16_round13: times 8 dd 0x02000 ;(1 << 13)
>> +pd_yuv2gbrp16_round13: times 8 dd 0xE0002000 ;(1 << 13) - (1 << 29)
>> pd_yuv2gbrp16_a_offset: times 8 dd 0x20002000
>> pd_yuv2gbrp16_upper30: times 8 dd 0x3FFFFFFF ;(1<<30) - 1
>> pd_yuv2gbrp16_upper27: times 8 dd 0x07FFFFFF ;(1<<27) - 1
>> +pd_yuv2gbrp16_upper16: times 8 dd 0x0000FFFF ;(1<<16) - 1
>>
>
> pd_yuv2gbrp16_upper16 doesn't appear to be used anywhere
>
nevermind, I see where it is used now.
>
>
>> pd_yuv2gbrp16_upperC: times 8 dd 0xC0000000
>> +pd_yuv2gbrp_debias: times 8 dd 0x00008000 ;(1 << 29 - 14)
>> pb_pack_shuffle8: db 0, 4, 8, 12, \
>> -1, -1, -1, -1, \
>> -1, -1, -1, -1, \
>> @@ -883,14 +885,26 @@ cglobal yuv2%1_full_X, 12, 14, 16, ptr, lumFilter,
>> lumSrcx, lumFilterSize, chrFi
>> paddd G, Y
>> paddd B, Y
>>
>> +%if DEPTH < 16
>> CLIPP2 R, 30
>> CLIPP2 G, 30
>> CLIPP2 B, 30
>> +%endif
>>
>> psrad R, RGB_SHIFT
>> psrad G, RGB_SHIFT
>> psrad B, RGB_SHIFT
>>
>> +%if DEPTH >= 16
>> + paddd R, [pd_yuv2gbrp_debias]
>> + paddd G, [pd_yuv2gbrp_debias]
>> + paddd B, [pd_yuv2gbrp_debias]
>> +
>> + CLIPP2 R, 16
>> + CLIPP2 G, 16
>> + CLIPP2 B, 16
>> +%endif
>> +
>> %if FLOAT
>> cvtdq2ps R, R
>> cvtdq2ps G, G
>> --
>> 2.17.1
>>
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